BIOSTATISTICS CORE DESCRIPTION: The Biostatistics Core will provide statistical expertise and develop methodology for the OPRC. It is presently staffed by two Ph.D. Research Scientists (Drs. Stoolmiller and Leve) who will provide 20 percent of their time each to this Core. A quarter-time data analyst will also assist. Dr. Leve is also listed on the Center's Theory Core and Dr. Stoolmiller is listed on the observation Core. Both of these researchers are also on the Center's Theory Core and Dr. Stoolmiller is listed on the Observation Core. Both of these researchers are also on the Center's Executive Committee. The unit is staffed with experienced faculty. They are well respective faculty in their areas and knowl3edged in developmental research and structural equation modeling.